Pros: not excessively revealing, smooth treble
Cons: it's not huge and doesn't weigh 100lbs. it's too small. Can't possibly sound good being so small.
NOTES: SKIP THIS FIRST PART
I had a heck of a time getting this to sound right. It made me aware of nearly THREE problems with my setup. Not even kidding. My desktop computer's rear USB port does not work with this. A powered USB hub is required. Next for some strange reason I have to use high gain on my Q701 with this dac and my Headroom Micro Amp. With 8% volume. If not, the Q701 is too fatiguing. This never occurred with my HRT MSII. On that, Medium was fine.
I'll keep this short (EDIT: whoops guess not). First impressions of this over my HRT MSII is that it sounds much more balanced. Yet strangely any of my garbage tracks suddenly don't sound so bad. It seems to take the edge off them. Why? I have no idea. On 5 of my CD players these same tracks are just awful and much worse. Way more fatiguing. I'm listening to a song right now that was unbearably bad on my HRT MSII and CD players and now it's quite listenable...even on the Q701. You could say those 5 players are just more revealing or colored, but that's unlikely to be true.
The idea that this makes the Q701 sound less warm or more revealing or analytical is nonsense. With my Q701 I still retained it's warm and full sound. If anything, it's treble is even more smooth and easier on the ears. The Q701 now sounds closer to neutral than before. I would say in comparison the HRT was a tad warmer, but only slightly. Again, it doesn't make the Q701 any leaner in the mids or anything like that. This is really the best i've ever heard the Q701.
I find the ODAC gave the Q701 a slightly larger soundstage with better imaging, but the difference isn't huge. I was actually confused with the difference in imaging. My X-Fi Go Pro does seem to give the Q701 a slightly larger soundstage than the ODAC. Don't really care though.
I actually find this DAC very musical and smooth sounding. Maybe it's the headphones and music too. All my garbage tracks are not put under the microscope at all. They sounded much worse on the HRT MSII. I actually think that thing might be more revealing of bad recordings.
I've not had this thing magically change any of my headphones in major ways. Generally they sound just like they should, but even better in many areas.
The biggest improvement in sound was with my $80 Koss Pro DJ100. Mostly improved soundstage size and better bass. Not more bass, but just better bass. I didn't even think that was possible since i've never heard the bass as good on any other DAC. I did experience a bit more detail with the DJ100, but I didn't feel ever that anything was being shoved in my face.
One reason I sold my HRT MSII is that I didn't like it with my HD-598 and HD-580. I just have weird preferences I guess. At first I blamed my amp, but i've found it's more transparent than I had originally thought. Less colored than the HRT MSII (which is still fairly neutral). The ODAC is really so much better IMO with my two Sennheiser headphones. It doesn't make them warmer or give them any extra bass. I think if I ever tried the HD-650 again, this is the DAC which would make me like it even more.
BTW it's general "signature" is close to my onboard sound, Sansa Clip+ and X-Fi Go Pro DAC. Obviously this is a huge upgrade, but all of them sound pretty flat to me. Blind A/B test would be stupid easy though.
SCIENCE GUYS IGNORE THIS NEXT PARAGRAPH:
I could never ever hear a difference in DIY (cheap) cables until I got my HRT MSII. It was stupid easy to tell the difference (less so with interconnect cables). Nothing major. With this I can't hear an ounce of difference. Only if the cable is a very high capacitance wire (such as Canare). My guess is that the ODAC is just no super duper revealing detail monster like the HRT. No idea here. I'm perfectly happy with my $1 Monoprice cables. Consider this a bonus. I can't really figure this one out (for myself).
Now that i've found a budget amp that plays well with EVERY headphone i've ever tried, I think i've finally found the DAC to go with it. I don't know why, but every single popular amp or DAC on Head-Fi i've tried has had some weird coloration to it or only sounds best with specific headphones. I hate that. Maybe I just have very bad luck. I'd also prefer to not feel the need to buy a DAC/amp every year and would rather spend that on headphones or new music.
BTW I think maybe this has very slightly rolled off highs. Probably not, but I guess it's possible. Not like the E10 though...this seems far more balanced than the E10. E10 didn't sound neutral, yet measures flat. Strange.
I've now been using this since 8/20. Never imagined it'd be such a nice upgrade from my HRT MSII, but it is. Unlike the HRT, this thing (like my amp) plays well with every headphone. Sounds equally good with every single thing.
Lately I did notice that it's even less warm sounding than my Clip+. I took my KRK KNS-8400 downstairs to my main setup and it just wasn't the same, but still good. Yeah..I just called the Clip+ warm sounding!
I'd say my favorite headphone with the ODAC is the Q701.
For the record, I still don't find the ODAC excessively detailed or too analytical. Detail level is just where it should be. The HRT did seem to be more detailed. Why? Not sure. Maybe it's just due to a little more coloration and my brain being fooled. Who knows..
With this ODAC, my Q701 sounds as smooth as the HD-598. Nothing in it's frequency jumping out at me too much. Not thin or analytical, but quite musical.